1. Field of the Invention
The present invention relates to a metal separator for a fuel cell and a bonding method there of.
2. Description of the Prior Arts
Recently, a metallic separator has been developed in addition to a carbonate one as a separator for a fuel cell. The metallic separator has low-thermal capacity to thereby be capable of rapidly raising a temperature in a fuel cell stack to a suitable temperature upon its starting-up. The metallic separator is comprised of two plate-like separator members bonded to each other via an electrolyte film, an anode electrode and a cathode electrode to form introducing sections of hydrogen gas and oxidant gas. A plurality of spaces formed between a pair of the metallic separators are used as cooling water paths for cooling the fuel cell stack.
There are several types of methods for bonding two plate-like members, among which a method using a binder, a method by a brazing and a method utilizing a diffusion of a metallic material are mainly adopted. Incidentally, the electric power generation efficiency of the fuel cell is reduced when there is a deviation between the introducing sections of hydrogen gas and oxidant gas. Therefore, the deviation amount between two separator members is strictly placed to an amount not more than a predetermined amount upon bonding two separator members to each other. However, in any one of the above-mentioned methods, both of two separator members have to be left to stand for a long period with both of them brought into intimate contact upon bonding two separator members to each other, resulting in involving difficulty to perform a positional alignment for preventing the deviation between them. Therefore, a positioning member or the like is required to be provided upon bonding the separators.
Further, the method for bonding with a binder performs a positional alignment between two separators having the binder applied thereon, and requires to leave two separators for several hours that are brought into intimate contact with each other for curing the binder, thus causing poor productivity. Moreover, it is necessary to select a binder tolerable to a tough temperature condition, since the fuel cell stack is under a high temperature. Additionally, the method by a brazing and the method utilizing a diffusion of the metallic material makes a production in a lot, thereby causing poor productivity and moreover, being likely to cause a separation, deviation, falling or the like at the bonding section by the deformation of the separator due to the temperature change of the fuel cell stack.